If you are using modern, hardened, quality films from Kodak, Ilford or Fuji, you will absolutely not get reticulation, or other ill effects from temp swings of +/- a couple of degrees throughout the process. However the post above suggesting you can have any temperature after development, and that 140F is an acceptable temperature, is very wrong. That is an enormous swing from any temperature normally used in film processing. Furthermore at such a high temperature the wet emulsion would be extremely fragile at best, making defects essentially inevitable.
Best practice is to keep the entire process including the wash as consistent in temperature as possible. This need not be 68F. It can be anywhere in the 70s as long as you adjust your times accordingly (and avoid development times shorter than say 5 minutes).
For higher temperature conditions (example - tropical areas) there are special procedures, additives, and chemicals that can be used but I'm not familiar enough with any of them to make any recommendations.